TRAVERSE CITY, Mich. -- A fast-spreading aquatic virus threatening stormy waters for the Great Lakes fishing industry has been detected in Lake Huron for the first time, officials said Thursday.

The Michigan Department of Natural Resources said it had confirmed the presence of viral hemorrhagic septicema, or VHS, in fish samples from waters as far north as Cheboygan -- only about 15 miles from where Lake Huron meets Lake Michigan.

VHS previously had been found in only two of the Great Lakes -- Ontario and Erie -- and in Lake St. Clair, which links lakes Erie and Huron. But officials have predicted the virus eventually would spread across the entire lakes system, where the $4.5 billion fishery is a crucial segment of the economy.

"This disease threatens the closure of a major portion of the Michigan baitfish industry," said Chris Weeks, president of the Michigan Aquaculture Association. "It is also expected to have significant impacts on the aquaculture industry and Michigan's recreational fisheries."

How damaging the virus turns out to be will depend largely on whether fish develop immunity to it, said Kelley Smith, chief of the DNR's fisheries division.

The virus poses no danger to people but is deadly for fish. It targets some of the region's most popular sport and commercial species.

Analyses completed earlier this week found VHS in whitefish from the Cheboygan area, whitefish and walleye from Thunder Bay, and Chinook salmon from a DNR egg-taking station near Rogers City, Smith said.

Originally a saltwater virus, VHS made its first known appearance in the Great Lakes in 2005, killing the likes of freshwater drum and muskellunge.

The Cheboygan-area whitefish were collected in 2005 during a survey for bacterial kidney disease, Smith said. They were examined again more recently and found to have carried VHS.

How VHS arrived in the lakes is uncertain. But fishery managers say a likely culprit is ballast water dumped by ocean freighters, widely considered a leading source of exotic species in the lakes.

"These new discoveries are extremely unfortunate and further highlight the problems created by the constant introductions of new diseases from outside the Great Lakes region," DNR Director Rebecca Humphries said.

The U.S. Department of Agriculture last October banned interstate shipments of 37 species of live fish from the Great Lakes region in hopes of checking the spread of VHS and keeping it out of inland waters.

After an outcry from fish farmers and bait fish dealers, the agency modified its emergency order to allow taking some fish across state lines with proper documentation. It will stay in place until federal and state authorities finish crafting a long-term policy.

The USDA's Animal and Plant Health Inspection Service has conducted several public hearings, including one in Romulus earlier this month.

"This is a highly contagious disease and we understand the importance of getting this rule out as quickly as we can," APHIS spokeswoman Karen Eggert said.

The confirmation that VHS has reached Lake Huron won't prompt any immediate policy changes on the federal level, Eggert said.

Meanwhile, the DNR said it would step up fish sampling in Lake Huron and the St. Marys River, which links lakes Huron and Superior. Chinook salmon in state hatcheries will be tested.

The DNR also said live fish no longer would be trapped and transferred from Michigan's Great Lakes waters for stocking programs unless they have tested negative for VHS. And it urged anglers not to move live fish between the Great Lakes and inland waters.

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Editor's Note -- John Flesher is the AP correspondent in Traverse City and has covered environmental issues since 1992.